Laser processing system, jet observation apparatus , laser processing method, and jet observation method

ABSTRACT

A laser processing system that can effectively blow out a material of a workpiece melted by a laser beam by effectively utilizing an assist gas emitted from a nozzle. The laser processing system comprises a nozzle including an emission opening configured to emit a jet of an assist gas along an optical axis of a laser beam, the nozzle being configured to forming a maximum point of velocity of the jet at a position away from the emission opening; a measuring instrument configured to measure the velocity of the jet; and a position acquisition section configured to acquire information representing a position of the maximum point based on output data of the measuring instrument.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a new U.S. Patent Application that claims benefit ofJapanese Patent Application No. 2018-157814, dated Aug. 24, 2018, thedisclosure of this application is being incorporated herein by referencein its entirety for all purposes.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a laser processing system, a jetobservation apparatus, a laser processing method, and a jet observationmethod.

2. Description of the Related Art

A laser processing system has been known that includes a nozzle that,when processing a workpiece with a laser beam, emits an assist gas forblowing out a material of a workpiece that is melted by the laser beam(e.g., JP 2017-051965 A).

There has been a need for a laser processing system that can effectivelyblow out a material of a workpiece that is melted by a laser beam byeffectively utilizing an assist gas emitted from a nozzle.

SUMMARY OF THE INVENTION

In an aspect of the present disclosure, a laser processing systemcomprises a nozzle including an emission opening configured to emit ajet of an assist gas along an optical axis of a laser beam, the nozzlebeing configured to forming a maximum point of velocity of the jet at aposition away from the emission opening; a measuring instrumentconfigured to measure the velocity of the jet; and a positionacquisition section configured to acquire information representing aposition of the maximum point based on output data of the measuringinstrument.

In another aspect of the present disclosure, a jet observation apparatuscomprises a measuring instrument configured to consecutively measurevelocity of a jet of a gas emitted from an emission opening of a nozzle,along the jet; and a position acquisition section configured to acquire,as information representing a position of a maximum point of thevelocity of the jet, a peak value of consecutive output data output bythe measuring instrument, the maximum point being formed at the positionaway from the emission opening.

In still another aspect of the present disclosure, a method of laserprocess on a workpiece using the above-mentioned laser processingsystem, comprises emitting the jet from the emission opening of thenozzle and processing the workpiece with the laser beam, while disposingthe nozzle (24) with respect to a process portion of the workpiece at atarget position determined based on the information.

In still another aspect of the present disclosure, a method of observinga jet, the method comprising consecutively measuring velocity of a jetof a gas emitted from an emission opening of a nozzle, along the jet;and acquiring, as information representing a position of a maximum pointof the velocity of the jet, a peak value of data obtained by consecutivemeasurement, the maximum point being formed at the position away fromthe emission opening.

According to the present disclosure, since the assist gas emitted fromthe nozzle during the process on the workpiece can be blown to theworkpiece at a velocity which is sufficiently large, it is possible toeffectively utilize the assist gas so as to effectively blow out amaterial of the workpiece melted by the laser beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a laser processing system.

FIG. 2 is an image obtained by capturing a jet of an assist gas emittedfrom a nozzle with a high-speed camera.

FIG. 3 is a diagram for illustrating a maximum point of velocity of ajet, an upper graph schematically shows a relationship between thevelocity of the jet and a position x from an emission opening, and theimage of FIG. 2 is shown below the graph.

FIG. 4 is a diagram of a jet observation apparatus.

FIG. 5 is a block diagram of the jet observation apparatus illustratedin FIG. 4 .

FIG. 6 is a diagram of another jet observation apparatus.

FIG. 7 is a block diagram of the jet observation apparatus illustratedin FIG. 6 .

FIG. 8 is a diagram of yet another jet observation apparatus.

FIG. 9 is a block diagram of the jet observation apparatus illustratedin FIG. 8 .

FIG. 10 is a diagram of another laser processing system.

FIG. 11 is a block diagram of the laser processing system illustrated inFIG. 10 .

FIG. 12 is a diagram of yet another laser processing system.

FIG. 13 is a block diagram of the laser processing system illustrated inFIG. 12 .

FIG. 14 is a flowchart illustrating an example of an operation flow ofthe laser processing system illustrated in FIG. 12 .

FIG. 15 is a flowchart illustrating an example of the flow of Step S14in FIG. 14 .

FIG. 16 is a graph schematically showing a relationship between outputdata of a measuring instrument illustrated in FIG. 12 and a distancefrom an emission opening.

FIG. 17 is a diagram of yet another laser processing system.

FIG. 18 is a block diagram of the laser processing system illustrated inFIG. 17 .

FIG. 19 is a diagram of yet another laser processing system.

FIG. 20 is a block diagram of the laser processing system illustrated inFIG. 19 .

FIG. 21 is a flowchart illustrating an example of an operation flow ofthe laser processing system illustrated in FIG. 19 .

FIG. 22 is a diagram of a jet adjustment device.

FIG. 23 illustrates an example of a mechanism section illustrated inFIG. 22 .

FIG. 24 illustrates another example of the mechanism section illustratedin FIG. 22 .

FIG. 25 is a diagram of yet another laser processing system.

FIG. 26 is a block diagram of the laser processing system illustrated inFIG. 25 .

FIG. 27 is a flowchart illustrating an example of an operation flow ofthe laser processing system illustrated in FIG. 25 .

FIG. 28 illustrates an example of a measuring instrument.

FIG. 29 illustrates another example of the measuring instrument.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described in detail belowwith reference to the drawings. Note that, in the various embodimentsdescribed below, the same reference numerals will be given to similarelements, and redundant descriptions thereof will be omitted. First, alaser processing system 10 will be described with reference to FIG. 1 .

The laser processing system 10 includes a laser oscillator 12, a laserprocessing head 14, an assist gas supply device 16, and a positioningdevice 18. The laser oscillator 12 oscillates a laser inside thereof,and emits a laser beam to the outside. The laser oscillator 12 may be ofany type, such as a CO₂ laser oscillator, a solid-state laser (YAGlaser) oscillator, or a fiber laser oscillator.

The laser processing head 14 includes a head main body 20, opticallenses 22, a lens driver 23, and a nozzle 24. The head main body 20 ishollow, and an optical fiber 26 is connected to a proximal end of thehead main body 20. The laser beam emitted from the laser oscillator 12propagates inside the optical fiber 26 and enters inside of the headmain body 20.

The optical lenses 22 include e.g. a collimating lens and a focusinglens, collimate and focus the laser beam entering into the head mainbody 20, and irradiate the laser beam onto a workpiece W. The opticallenses 22 are housed in the head main body 20 so as to be movable in adirection of an optical axis O.

The lens driver 23 moves each optical lens 22 in the direction of theoptical axis O. The lens driver 23 adjusts a position of each opticallens 22 in the direction of the optical axis O, whereby it is possibleto control a position of a focal point of the laser beam emitted fromthe nozzle 24 in the direction of the optical axis O.

The nozzle 24 is hollow and provided at a distal of the head main body20. The nozzle 24 has a truncated conical outer shape in which across-sectional area orthogonal to the optical axis O decreases as itextends from the proximal end toward the distal end, and has a circularemission opening 28 at the distal end thereof. A hollow chamber 29 isformed inside the nozzle 24 and the head main body 20. The laser beampropagating from the optical lens 22 is emitted from the emissionopening 28.

The assist gas supply device 16 supplies an assist gas to the chamber 29formed in the nozzle 24 and the head main body 20 via a gas supply tube30. The assist gas is e.g. nitrogen or air. The assist gas supplied tothe chamber 29 is emitted, as a jet, from the emission opening 28together with the laser beam along the optical axis O of the laser beam.The nozzle 24 forms a maximum point of velocity of the jet at a positionaway from the emission opening 28.

The jet of the assist gas emitted from the nozzle 24 will be describedbelow with reference to FIG. 2 and FIG. 3 . FIG. 2 is an image capturedby a high-speed camera imaging the jet emitted from the emission opening28 of the nozzle 24. FIG. 3 shows the image of the jet shown in FIG. 2and a graph schematically showing a relationship between velocity V ofthe jet and position x in a direction away from the emission opening 28along the optical axis O.

In this disclosure, the “velocity” of the jet is defined as a parameterincluding a flow velocity (unit: m/sec) and a flow rate (unit: m³/sec)of the assist gas. The jet shown in FIG. 2 and FIG. 3 is formed under acondition in which the supply pressure to the chamber 29 is 1 MPa, andthe opening dimension (diameter) of the emission opening 28 is 2 mm.

As shown in FIG. 2 and FIG. 3 , in the jet of the assist gas emittedfrom the nozzle 24, a first Mach disk region 33 and a second Mach diskregion 35, where the velocity V of the jet becomes local maximum, areformed at positions away from the emission opening 28 in the directionof the optical axis O. The position x₁ of the first maximum point 32 ofthe velocity V is included in the first Mach disk region 33, while theposition x₂ of the second maximum point 34 of the velocity V is includedin the second Mach disk region 35.

More specifically, as shown in the graph of FIG. 3 , the velocity V ofthe jet gradually increases as a distance from the position of theemission opening 28 (i.e., x=0) along the optical axis O increases, andreaches the first maximum point 32 at the position x₁. Note that, in thejet in the image shown in FIG. 3 , x₁≈4 mm. In the first Mach diskregion 33 including the position x₁, a so-called Mach disk, wherereflected waves of the assist gas reflected at a boundary between thejet and an atmosphere outside the jet interfere and strengthen with eachother, is formed.

The velocity V rapidly decreases as the distance in the direction awayfrom the emission opening 28 from the position x₁ along the optical axisO further increases, then turns to increase, and reaches the secondmaximum point 34 at the position x₂. In the second Mach disk region 35including the position x₂, a second Mach disk is formed.

Thus, in the jet emitted from the nozzle 24, a plurality of Mach disksare formed in the direction of the optical axis O, whereby the velocityV of the jet has a plurality of maximum points 32 and 34 in thedirection of the optical axis O. The number of the Mach disks (i.e.,maximum points) to be formed increases depending on the velocity V ofthe emitted jet.

In the present disclosure, when the laser processing system 10 carriesout laser process on the workpiece W, the nozzle 24 is disposed withrespect to a process portion S of the workpiece W at a target positiondetermined based on the position x₁ or x₂ of the maximum point 32 or 34,such that the workpiece W (specifically, the process portion S of theworkpiece W) is disposed in one of the Mach disk regions 33 and 35.

In the prior art, it has been considered preferable that the pressure ofthe assist gas blown to the workpiece W during the laser process on theworkpiece W is as large as possible. The pressure of the assist gas ismaximized at the position of the emission opening 28. Accordingly, inthe prior art, when laser-processing the workpiece W, the workpiece Whas been arranged as close as possible to the emission opening 28 atwhich the pressure is maximized. Specifically, in the prior art, theworkpiece W has been disposed in a proximity region 36 in FIG. 3 . Thisproximity region 36 is a region closer to the emission opening 28 thanthe first maximum point 32, wherein the pressure of the assist gas isalmost a maximum value in this proximity region 36.

When the nozzle 24 and the workpiece W are thus arranged closer to eachother and the laser process is carried out while the nozzle 24 is movedat high speed with respect to the workpiece W, plasma may be generatedeasier between the nozzle 24 and the workpiece W. When such plasma isgenerated, a finished surface of the workpiece W may become rough.Furthermore, when the nozzle 24 and the workpiece W are arranged closerto each other, particles of the workpiece W, that are melted andscattered by the laser process, may enter into the nozzle 24 through theemission opening 28, whereby a component (e.g., a protective glass) ofthe laser processing head 14 is more likely to be contaminated.

After diligent researching, the inventor obtained a knowledge that, asthe velocity V of the assist gas blown to the workpiece W during thelaser process on the workpiece W increases, the material of theworkpiece W melted by the laser beam can be more effectively blown outby the assist gas.

Based on this knowledge, the present inventor focused on a fact that theabove-described maximum points 32 and 34 are formed when the jet of theassist gas is emitted from the emission opening 28 of the nozzle 24, andfound that, if the workpiece W is disposed in one of the Mach diskregions 33 and 35 during the laser process on the workpiece W, theassist gas can be blown to the workpiece W at the velocity V greaterthan that in the proximity region 36 to the emission opening 28.

Referring again to FIG. 1 , the positioning device 18 disposes thenozzle 24 with respect to the process portion S at the target positiondetermined based on the position x₁ of the maximum point 32 or theposition x₂ of the maximum point 34, in order to dispose the workpiece W(e.g., process portion S) in the Mach disk region 33 or 35.Specifically, the positioning device 18 includes a work table 38, ay-axis movement mechanism 40, an x-axis movement mechanism 42, and az-axis movement mechanism 44.

The work table 38 is fixed on a floor of a work cell. For example, thework table 38 has a plurality of needles extending in the z-axisdirection in FIG. 1 , and the workpiece W is installed on aninstallation surface defined by tips of the plurality of needles. Thez-axis direction is substantially parallel to a vertical direction, forexample.

The y-axis movement mechanism 40 includes a pair of rail mechanisms 46and 48, and a pair of columns 50 and 52. Each of the rail mechanisms 46and 48 includes e.g. a servo motor and a ball screw mechanism (both notillustrated) therein, and extends in the y-axis direction. The railmechanisms 46 and 48 move the columns 50 and 52 in the y-axis direction,respectively.

The x-axis movement mechanism 42 includes e.g. a servo motor and ballscrew mechanism (both not illustrated) therein, and is fixed to thecolumns 50 and 52 so as to extend between the columns 50 and 52. Thex-axis movement mechanism 42 moves the z-axis movement mechanism 44 inthe x-axis direction. The z-axis movement mechanism 44 includes e.g. aservo motor and a ball screw mechanism (both not illustrated) therein,and moves the laser processing head 14 in the z-axis direction. Thelaser processing head 14 is provided at the z-axis movement mechanism 44such that the optical axis O of the laser beam to be emitted is parallelto the z-axis.

When the workpiece W is processed, the positioning device 18 disposesthe nozzle 24 at the target position with respect to the process portionS. For example, a below-described controller (not illustrated) providedin the laser processing system 10 controls the positioning device 18 soas to automatically dispose the nozzle 24 with respect to the workpieceW at the target position. Alternatively, an operator may manuallyoperate the positioning device 18 so as to dispose the nozzle 24 withrespect to the process portion S at the target position.

Then, the assist gas supply device 16 supplies the assist gas to thechamber 29, and emits the jet of the assist gas, which has the Mach diskregions 33 and 35, from the emission opening 28. Then, the laseroscillator 12 emits the laser beam to the laser processing head 14, andthe laser processing head 14 emits the laser beam from the emissionopening 28 so as to irradiate the workpiece W. At this time, the lensdriver 23 adjusts the position of each optical lens 22 in the directionof the optical axis O, such that the focal point of the laser beamemitted from the emission opening 28 is located at the process portionS.

In this way, the workpiece W is laser-processed in a stated where theworkpiece W is disposed in the Mach disk region 33 or 35 of the jet.According to this configuration, since the assist gas emitted from thenozzle 24 can be blown to the workpiece W at the velocity V greater thanthat in the proximity region 36 of the emission opening 28 during theprocess on the workpiece W, it is possible to effectively make use ofthe assist gas so as to effectively blow out the material of theworkpiece W melted by the laser beam.

Furthermore, it is possible to prevent the above-described plasma frombeing generated when compared to a case where the workpiece W isdisposed in the proximity region 36 to the emission opening 28, as aresult of which, the finishing quality of the workpiece W can beimproved. In addition, it is possible to prevent the scattered particlesof the workpiece W generated during the laser process from entering intothe nozzle 24 when compared to the case where the workpiece W isdisposed in the proximity region 36, as a result of which, thecontamination of the component of the laser processing head 14 can beprevented.

Next, a jet observation apparatus 60 will be described with reference toFIG. 4 and FIG. 5 . The jet observation apparatus 60 acquiresinformation representing the position x₁, x₂ of the above-describedmaximum point 32, 34. The jet observation apparatus 60 includes acontroller 62, a dummy workpiece 64, a measuring instrument 66, and theabove-described positioning device 18. The controller 62 includes aprocessor (CPU, GPU, etc.) and a storage (ROM, RAM, etc.), and controlsthe measuring instrument 66 and the positioning device 18.

The dummy workpiece 64 is installed on the installation surface of thework table 38. The dummy workpiece 64 has an outer shape (dimensions)the same as the workpiece W, and includes a dummy process portion 64 acorresponding to the process portion S. In an example illustrated inFIG. 4 , the dummy workpiece 64 is disposed at a position different fromthe installation position of the workpiece W during the laser process.

The measuring instrument 66 measures the velocity V of the jet emittedfrom the emission opening 28, at a position of the dummy process portion64 a (or a position slightly displaced from the dummy process portion 64a in a direction toward the emission opening 28). For example, themeasuring instrument 66 includes a hot-wire anemometer configured tomeasure the velocity V in a contact manner, wherein the hot-wireanemometer includes a hot-wire which is disposed in the jet and theresistance value of which varies in response to the velocity V.Alternatively, the measuring instrument 66 includes a laser anemometerconfigured to measure the velocity V in a non-contact manner, whereinthe laser anemometer includes an optical sensor configured to irradiatethe jet with light and measure the velocity V.

The measuring instrument 66 measures the velocity V of the jet, andoutputs it to the controller 62 as output data (measured values) a. Themeasuring instrument 66 may be disposed on the dummy workpiece 64, ormay be disposed separate away from the dummy workpiece 64. The dummyworkpiece 64 is disposed at forward (i.e., downstream) in the flowdirection of the jet, and the measuring instrument 66 measures thevelocity V at a position between the emission opening 28 and the dummyworkpiece 64.

The positioning device 18 includes the work table 38, the y-axismovement mechanism 40, the x-axis movement mechanism 42, and the z-axismovement mechanism 44, and moves the laser processing head 14 in thex-axis, y-axis, and z-axis directions so as to move the laser processinghead 14 with respect to the dummy workpiece 64 and the measuringinstrument 66.

Next, a method of acquiring the position x₁, x₂ of the maximum point 32,34 using the jet observation apparatus 60 will be described. First, thecontroller 62 operates the positioning device 18 so as to dispose thelaser processing head 14 at an initial measuring position. When thelaser processing head 14 is disposed at the initial measuring position,the laser processing head 14 is positioned with respect to the dummyworkpiece 64 and the measuring instrument 66, such that the optical axisO of the laser processing head 14 intersects the dummy process portion64 a of the dummy workpiece 64, as illustrated in FIG. 4 .

Also, a distance d_(a) between the emission opening 28 and a measuringposition of the measuring instrument 66 (i.e., the position of the dummyprocess portion 64 a) is an initial value d_(a0). As an example, theinitial value d_(a0) is set such that the measuring position of themeasuring instrument 66 is disposed at a position close to the emissionopening 28, such as the proximity region 36 in FIG. 3 .

As another example, the initial value d_(a0) is set such that themeasuring position of the measuring instrument 66 is disposed at aposition sufficiently separate to downstream of the jet from a positionwhere a maximum point farthest from the emission opening 28 (in theexample of FIG. 3 , the second maximum point 34) is estimated to belocated. The initial value d_(a0) is predetermined by the operator.

Then, the controller 62 sends a command to the assist gas supply device16, and in response to the command, the assist gas supply device 16supplies the assist gas to the chamber 29 at a supply pressure P_(s).The nozzle 24 emits the jet of the assist gas having the maximum points32 and 34 of the velocity V, as shown in FIG. 2 and FIG. 3 .

Then, the controller 62 operates the positioning device 18 so as to movethe laser processing head 14 in the z-axis direction so as to change thedistance d_(a) between the emission opening 28 and the measuringposition of the measuring instrument 66. As an example, if theabove-described initial value d_(a0) is set to dispose the measuringposition of the measuring instrument 66 at the close position to theemission opening 28, the controller 62 operates the positioning device18 so as to move the laser processing head 14 in the z-axis positivedirection to increase the distance d_(a).

As another example, if the above-described initial value d_(a0) is setto dispose the measuring position of the measuring instrument 66 atdownstream side of the maximum point farthest from the emission opening28, the controller 62 operates the positioning device 18 so as to movethe laser processing head 14 in the z-axis negative direction todecrease the distance d_(a).

While the positioning device 18 moves the laser processing head 14 inthe z-axis direction, the controller 62 sends a command to the measuringinstrument 66 and cause the measuring instrument 66 consecutivelymeasure the velocity V. For example, the measuring instrument 66consecutively measures the velocity V at a predetermined period (e.g.,0.5 seconds) while the positioning device 18 moves the laser processinghead 14. In this way, the measuring position of the measuring instrument66 is moved relatively along the jet, and the measuring instrument 66consecutively measures the velocity V along the jet.

The measuring instrument 66 outputs the measured velocity V as theoutput data α (=V) to the controller 62. A relationship between theoutput data α, which is outputted by the measuring instrument 66 in thisway, and the distance d_(a) corresponds to the relationship between thevelocity V and the position x shown in FIG. 3 . That is, the output dataα acquired by the measuring instrument 66 changes in response to thedistance d_(a), and has a first peak value α_(max1) at a positioncorresponding to the first maximum point 32 and a second peak valueα_(max2) at a position corresponding to the second maximum point 34.

The controller 62 acquires the first peak value α_(max1) of theconsecutive output data α outputted by the measuring instrument 66 asinformation representing the position x₁ of the first maximum point 32,and acquires the second peak value α_(max2) as information representingthe position x₂ of the second maximum point 34. In this way, thecontroller 62 functions as a position acquisition section 68 configuredto acquire the information representing the position of the maximumpoint 32, 34 based on the output data α.

Then, the controller 62 acquires, as a target distance d_(T), thedistance d_(a) between the measuring position of the measuringinstrument 66 (i.e., the position of the dummy process portion 64 a) andthe emission opening 28 when the first peak value_(amaxi) is measured.This target distance d_(T) represents the position of the first maximumpoint 32 with respect to the emission opening 28, and can be acquired bye.g. a known gap-sensor, a displacement measuring instrument, or thelike.

Then, the controller 62 resisters the target distance d_(T) in a database in association with the opening dimension ϕ of the emission opening28 and the supply pressure P_(s) when measuring the velocity V, andstores it in the storage. The operator changes the opening dimension ϕof the nozzle 24 and the supply pressure P_(s) in various ways, and thecontroller 62 acquires the target distance d_(T) and registers it in thedatabase of the above-described method, each time the opening dimensionϕ and the supply pressure P_(s) are changed. Note that, if the emissionopening 28 is circular, the opening dimension is a diameter.

Table 1 below shows an example of the database of the opening dimensionϕ, the supply pressure P_(s), and the target distance d_(T).

TABLE 1 Supply Pressure P_(s) 0.8 MPa . . . 2.0 MPa Opening dimension ϕϕ1.0 d_(T) = 4 mm . . . d_(T) = 6 mm . . . . . . . . . . . . ϕ4.0 d_(T)= 6 mm . . . d_(T) = 10 mm 

In the database shown in Table 1, a plurality of the target distancesd_(T) are set in association with the opening dimension ϕ of the nozzle24 and the supply pressure P_(s). Note that, the controller 62 mayacquire, as a second target distance d_(T2), a distance d_(a2) betweenthe emission opening 28 and the measuring position of the measuringinstrument 66 when the second peak value α_(max2) is measured, and maysimilarly create a database of the second target distance d_(T_2).Further, different databases may also be created for different kinds ofthe assist gas (nitrogen, air, etc.).

The database of the target distance d_(T) created in this manner is usedto determine a target position at which the nozzle 24 is to be disposedwhen the laser process is carried out onto the workpiece W in the laserprocessing system as described below. For example, if the openingdimension ϕ of the emission opening 28 of the nozzle 24 used during thelaser process is 4 mm and the supply pressure P_(s) to the chamber 29 is2.0 MPa, the data of d_(T)=10 mm is used to determine the targetposition.

In this way, by measuring the velocity V of the jet of the assist gas,the information representing the position of the maximum point 32, 34can be acquired. According to this configuration, it is possible toobtain the position of the maximum point 32, 34 with high accuracy bymeasurement.

In addition, the jet observation apparatus 60 includes the dummyworkpiece 64. In this regard, when the laser process is actually carriedout, the assist gas is blown onto the workpiece W. In the jetobservation apparatus 60, the assist gas is blown onto the dummyworkpiece 64 instead of the workpiece W, and the positions of themaximum points 32 and 34 are measured from the velocity V measured atthe position of the dummy process portion 64 a of the dummy workpiece64. According to this configuration, since the position of the maximumpoint 32, 34 can be measured in a state analogous to actual the laserprocess, it is possible to measure the position of the maximum point 32,34 with higher accuracy.

Further, the dummy workpiece 64 has an outer shape (dimensions) the sameas the workpiece W. According to this configuration, since the positionof the maximum point 32, 34 can be measured in a state significantlyanalogous to actual laser processing, it is possible to measure theposition of the maximum point 32, 34 with further higher accuracy. Notethat, the dummy workpiece 64 may have an outer shape (dimensions)different from the workpiece W. In this case, the dummy workpiece 64 mayhave a thickness in the z-axis direction the same as that of theworkpiece W, and include the portion 64 a corresponding to the processportion S. Also, the position of the maximum point 32, 34 can beacquired without the dummy workpiece 64.

Then, a jet observation apparatus 70 will be described with reference toFIG. 6 and FIG. 7 . The jet observation apparatus 70 acquires theabove-described information representing the position x₁, x₂ of themaximum point 32, 34. The jet observation apparatus 70 includes acontroller 72, a measuring instrument 76, and the positioning device 18.The controller 72 includes a processor and a storage (not illustrated),and controls the measuring instrument 76 and the positioning device 18.

The positioning device 18 includes the work table 38, the y-axismovement mechanism 40, the x-axis movement mechanism 42, and the z-axismovement mechanism 44, wherein an object 74 is installed on the worktable 38. The positioning device 18 moves the laser processing head 14in the x-axis, y-axis, and z-axis directions, thereby moving the nozzle24 with respect to the object 74.

A circular through hole 74 a is formed in the object 74. An openingdimension of the through hole 74 a is set to be substantially the sameas an opening dimension of a through hole that is estimated to be formedwhen the workpiece W is perforated by a laser beam emitted from thenozzle 24. The object 74 may have an outer shape (dimensions) the sameas the workpiece W, or have a different outer shape (dimensions) fromthe workpiece W. Furthermore, the object 74 may have a thickness in thez-axis direction the same as the workpiece W, and include a portioncorresponding to the process portion S.

The measuring instrument 76 is disposed adjacent to the through hole 74a, and measures a sound pressure SP or a frequency f of a soundgenerated by the jet emitted from the emission opening 28 of the nozzle24 impinging on the object 74 when passing through the through hole 74a. Note that, in the present disclosure, the “sound pressure” of thesound includes not only a sound pressure (unit: Pa), but also a soundpressure level (unit: dB), sound intensity (unit: W/m²), etc.

Further, the “frequency” of the sound includes not only the frequency ofthe sound, but also frequency characteristic of the sound (i.e., afrequency spectrum). The frequency characteristic includes informationsuch as a sound pressure level of at least one frequency component(e.g., 1 Hz), an average sound pressure level in a predeterminedfrequency band (e.g., 1 kHz to 10 kHz), etc. The measuring instrument 76includes a microphone 76 a configured to convert a sound into anelectrical signal, and a frequency acquisition section 76 b configuredto acquire a frequency characteristic of the sound from the electricalsignal.

Next, a method of acquiring the position x₁, x₂ of the maximum point 32,34 using the jet observation apparatus 70 will be described. First, thecontroller 72 operates the positioning device 18 so as to dispose thelaser processing head 14 at an initial measuring position. When thelaser processing head 14 is disposed at the initial measuring position,the laser processing head 14 is positioned with respect to the object 74such that the optical axis O of the laser processing head 14 passesthrough the through hole 74 a, as illustrated in FIG. 6 . Additionally,a distance d_(b) between the emission opening 28 and the object 74 is aninitial value d_(b0).

As an example, the initial value d_(b0) is set such that the object 74is disposed at a position close to the emission opening 28, such as theproximity region 36 in FIG. 3 . As another example, the initial valued_(b0) is set such that the object 74 is disposed at a positionsufficiently separate to downstream side of the jet from a positionwhere a maximum point farthest from the emission opening 28 (in theexample of FIG. 3 , the second maximum point 34) is estimated to belocated.

Then, the controller 72 sends a command to the assist gas supply device16, and in response to the command, the assist gas supply device 16supplies the assist gas to the chamber 29 at the supply pressure P_(s).The nozzle 24 emits the jet of the assist gas having the maximum points32 and 34. Then, the controller 72 operates the positioning device 18 soas to move the laser processing head 14 in the z-axis direction tochange the distance d_(b) between the object 74 and the emission opening28.

As an example, if the above-described initial value d_(b0) is set so asto dispose the object 74 at the position close to the emission opening28, the controller 72 operates the positioning device 18 so as to movethe laser processing head 14 in the z-axis positive direction toincrease the distance d_(b).

As another example, if the above-described initial value d_(b0) is setso as to dispose the object 74 at downstream side of a maximum pointfarthest from the emission opening 28, the controller 72 operates thepositioning device 18 so as to move the laser processing head 14 in thez-axis negative direction to decrease the distance d_(b).

While the positioning device 18 moves the laser processing head 14 inthe z-axis direction to bring the nozzle 24 closer to or away from theobject 74, the controller 72 sends a command to the measuring instrument76 so as to cause the measuring instrument 76 to consecutively measurethe sound pressure SP or the frequency f. For example, the measuringinstrument 76 consecutively measures the sound pressure SP or thefrequency f at a predetermined period (e.g., 0.5 seconds) while thepositioning device 18 moves the laser processing head 14. The measuringinstrument 66 sequentially outputs the measured sound pressure SP or thefrequency f to the controller 72 as output data β (=SP or f).

The sound pressure SP and the frequency f of the sound generated by thejet impinging on the object 74 during passing through the through hole74 a are highly correlated with a flow velocity V_(s) of the assist gas.Specifically, the sound pressure (peak value, effective value, etc.) ofthe sound generated by the jet impinging on the object 74 and frequencycharacteristic of the sound (e.g., a sound pressure level of at leastone frequency component) are highly correlated with the flow velocityV_(s) of the assist gas.

Therefore, a relationship between the acquired output data β and thedistance d_(b) corresponds to the graph illustrated in FIG. 3 . That is,the output data β from the measuring instrument 76 changes in responseto the distance d_(b), and has a first peak value β_(max1) at a positioncorresponding to the first maximum point 32 and a second peak valueβ_(max2) at a position corresponding to the second maximum point 34.

The controller 72 acquires the first peak value β_(max1) of theconsecutive output data β outputted by the measuring instrument 76 asinformation representing the position x₁ of the first maximum point 32,and acquires the second peak value β_(max2) as information representingthe position x₂ of the second maximum point 34. In this way, thecontroller 72 functions as a position acquisition section 78 configuredto acquire the information representing the position of the maximumpoint 32, 34 based on the output data β.

Then, the controller 72 acquires, as the target distance d_(T), thedistance d_(b) between the object 74 and the emission opening 28 whenthe first peak value β_(max1) is measured. This target distance d_(T)represents the position of the first maximum point 32 with respect tothe emission opening 28, and can be acquired using e.g. a knowngap-sensor or the like.

Then, the controller 72 registers the target distance d_(T) and thefirst peak value β_(max1) in a database in association with the openingdimension ϕ of the emission opening 28 and the supply pressure P_(s)when the sound pressure SP and the frequency f are measured. Table 2below shows an example of the database of the opening dimension ϕ, thesupply pressure P_(s), the first peak value β_(max1), and the targetdistance d_(T).

TABLE 2 Supply Pressure P_(s) 0.8 MPa 2.0 MPa Peak . . . Peak ValueDistance . . . Value Distance Opening ϕ1.0 114 dB d = 4 mm . . . 120 dBd = 6 mm dimension ϕ . . . . . . . . . . . . . . . . . . ϕ4.0 110 dB d =6 mm . . . 117 dB d = 10 mm 

In the database shown in Table 2, the first peak value β_(max1) (soundpressure level) and the target distance d_(T) are registered inassociation with the opening dimension ϕ of the nozzle 24 and the supplypressure P_(s). Note that, the controller 72 may acquire, as a secondtarget distance d_(T_2), a distance d_(b_2) between the emission opening28 and the object 74 when the second peak value β_(max2) is measured,and may similarly create a database of the second target distanced_(T_2).

Further, a plurality of databases may also be created for respectivetypes of assist gas (nitrogen, air, etc.). The database of the targetdistance d_(T) created in this manner is used to determine a targetposition at which the nozzle 24 is to be disposed when the laser processis carried out onto the workpiece W in a laser processing system, asdescribed below.

As described above, according to the jet observation apparatus 70, theinformation representing the position x₁, x₂ of the maximum point 32, 34can be acquired, based on the sound generated when the jet of the assistgas impinges on the object 74. According to this configuration, it ispossible to obtain the position x₁, x₂ of the maximum point 32, 34 withhigh accuracy, by measurement. Further, the jet observation apparatus 70can acquire the information representing the position x₁, x₂ of themaximum point 32, 34 during the laser process, as described below.

Then, a jet observation apparatus 80 will be described with reference toFIG. 8 and FIG. 9 . The jet observation apparatus 80 acquires theabove-described position x₁ of the first maximum point 32, by apredetermined calculation. The jet observation apparatus 80 includes acontroller 82 and a measuring instrument 84. The controller 82 includesa processor and a storage (not illustrated), and controls the measuringinstrument 84.

The measuring instrument 84 measures a supply flow rate V_(v) of theassist gas supplied from the assist gas supply device 16 to the chamber29. The measuring instrument 84 is installed in the gas supply tube 30,and measures the flow rate V_(v) of the assist gas flowing through thegas supply tube 30 from the assist gas supply device 16 toward thechamber 29.

Next, a method of acquiring the position x₁ of the first maximum point32 by the jet observation apparatus 80 will be described. First, thecontroller 82 sends a command to the assist gas supply device 16, and inresponse to the command, the assist gas supply device 16 supplies theassist gas to the chamber 29. The nozzle 24 emits the jet of the assistgas having the maximum points 32 and 34.

Then, the controller 82 sends a command to the measuring instrument 84,and in response to the command, the measuring instrument 84 measures thesupply flow rate V_(v) from the assist gas supply device 16 to thechamber 29.

The measuring instrument 84 outputs output data (measurement value) ofthe supply flow rate V_(v) to the controller 82. Then, the controller 82calculates a distance d_(c) from the emission opening 28 to the firstmaximum point 32, as information of the position x₁ of the first maximumpoint 32, using the output data V_(v) from the measuring instrument 84and Equation 1 indicated below.d _(c)=0.67×ϕ×(ρV _(s) ²/2)^(1/2)  (Equation 1)

In the Equation 1, ϕ indicates the opening dimension of the emissionopening 28, ρ indicates a viscosity coefficient of the assist gas, andV_(s) indicates the flow velocity V_(s) of the assist gas obtained fromthe output data V_(v) and the opening dimension ϕ. In this way, thecontroller 82 functions as a position acquisition section 86 configuredto acquire the position x₁ of the first maximum point 32 by calculation,from the output data V_(v) of the measuring instrument 84.

According to the jet observation apparatus 80, it is possible to quicklyobtain the position x₁ of the first maximum point 32 with high accuracy,by calculation. Also, the jet observation apparatus 80 can acquire theposition x₁ of the first maximum point 32 in real-time during the laserprocess, as described below.

Next, a laser processing system 100 will be described with reference toFIG. 10 and FIG. 11 . The laser processing system 100 includes the laseroscillator 12, the laser processing head 14, the assist gas supplydevice 16, the positioning device 18, and a controller 102. Thecontroller 102 includes a processor (not illustrated) and a storage 104,and controls the laser oscillator 12, the laser processing head 14, theassist gas supply device 16, and the positioning device 18. The storage104 stores a database 106. The database 106 is one as shown in e.g.Table 1 or Table 2 described above.

Next, operation of the laser processing system 100 will be described.First, the controller 102 acquires setting values of the openingdimension ϕ of the emission opening 28 of the nozzle 24 to be used andthe supply pressure P_(s) of the assist gas from the assist gas supplydevice 16 to the chamber 29, and from the setting values of the openingdimension ϕ and the supply pressure P_(s), reads out from the storage104 and acquires the corresponding target distance d_(T) in the database106.

Then, the controller 102 operates the positioning device 18 so as tomove the laser processing head 14 with respect to the workpiece W todisposes the nozzle 24 at a target position where a distance d betweenthe emission opening 28 and the process portion S coincides with thetarget distance d_(T). In this way, the target position is determinedusing the database 106, and the controller 102 functions as a movementcontroller 108 configured to control the positioning device 18 (i.e.,the movement mechanisms 40, 42 and 44) so as to dispose the nozzle 24 atthe target position.

The controller 102 then operates the assist gas supply device 16 so asto supply the assist gas to the chamber 29 at the supply pressure P_(s),and the nozzle 24 emits the jet of the assist gas having the maximumpoints 32 and 34 of the velocity V. Then, the controller 102 operatesthe laser oscillator 12 so as to emit the laser beam from the emissionopening 28, and operates the lens driver 23 so as to adjust the positionof each optical lens 22 in the direction of the optical axis O such thatthe focal point of the emitted laser beam is positioned at the processportion S.

As a result, a through hole is formed at the process portion S of theworkpiece W by the laser beam, and the controller 102 operates thepositioning device 18 in accordance with a processing program stored inthe storage 104 so as to perform the laser process (specifically, lasercutting) on the workpiece W while moving the nozzle 24 with respect tothe workpiece W. At this time, the process portion S of the workpiece Wis disposed in the first Mach disk region 33 (specifically, the positionof the first maximum point 32) of the jet of the assist gas.

According to the laser processing system 100, it is possible toeffectively make use of the assist gas so as to effectively blow out thematerial of the workpiece W melted by the laser beam. In addition, sincethe above-described generation of the plasma can be prevented, it ispossible to improve finishing quality of the process portion S of theworkpiece W, and prevent contamination of the component of the laserprocessing head 14.

Further, in the laser processing system 100, the target position wherethe nozzle 24 is to be disposed during the process on the workpiece W isdetermined using the database 106 of the position of the first maximumpoint 32. According to this configuration, it is possible to quickly andeasily position the nozzle 24 and the workpiece W at the target positionto start the laser process.

Note that, in the laser processing system 100, the storage 104 may beprovided as a separate element from the controller 102. In this case,the storage 104 may be built in an external device (a server, etc.)communicatively connected to the controller 102, or may be a storagemedium (hard disk, flash memory, etc.) that can be externally attachedto the controller 102. Furthermore, the controller 102 may fix thedistance between the emission opening 28 and the workpiece W whenlaser-processing the workpiece W.

Next, a laser processing system 110 will be described with reference toFIG. 12 and FIG. 13 . The laser processing system 110 includes the laseroscillator 12, the laser processing head 14, the assist gas supplydevice 16, the positioning device 18, the measuring instrument 76, and acontroller 112.

The controller 112 includes a processor and the storage 104, andcontrols the laser oscillator 12, the laser processing head 14, theassist gas supply device 16, the positioning device 18, and themeasuring instrument 76. The database 106 as shown in above Table 2 isstored in the storage 104. The controller 112 functions as theabove-described position acquisition section 78. Accordingly, in thelaser processing system 110, the positioning device 18, the measuringinstrument 76, and the controller 112 constitute the jet observationapparatus 70 described above.

Then, operation of the laser processing system 110 will be describedwith reference to FIG. 14 . A flow illustrated in FIG. 14 is startedwhen the controller 112 receives a processing start command from anoperator, a host controller, or a processing program.

In step S1, the controller 112 disposes the nozzle 24 at an initialtarget position with respect to the process portion S. Specifically, thecontroller 112 acquires the setting values of the opening dimension ϕ ofthe emission opening 28 of the nozzle 24 to be used and the supplypressure P_(s) of the assist gas to the chamber 29, and from the settingvalues of the opening dimension ϕ and the supply pressure P_(s), readsout and acquires the corresponding target distance d_(T) in the database106. Then, the controller 112 functions as the movement controller 108and operates the positioning device 18 so as to move the laserprocessing head 14 with respect to the workpiece W to dispose the nozzle24 at the initial target position where a distance d between theemission opening 28 and the process portion S coincides with the targetdistance d_(T).

In step S2, the controller 112 supplies the assist gas from the assistgas supply device 16 to the chamber 29 at the supply pressure P_(s), soas to emit the jet of the assist gas from the emission opening 28. Then,the controller 112 operates the laser oscillator 12 so as to emit thelaser beam from the emission opening 28, and operates the lens driver 23so as to adjust the position of each optical lens 22 in the direction ofthe optical axis O such that the focal point of the emitted laser beamis positioned at the process portion S. As a result, a through hole H(FIG. 12 ) is formed in the workpiece W, and the jet passes through thethrough hole H. This through hole H corresponds to the above-describedthrough hole 74 a.

In step S3, the controller 112 starts measurement by the measuringinstrument 76. Specifically, the controller 112 sends a command to themeasuring instrument 76, and in response to the command, the measuringinstrument 76 consecutively (e.g., at a predetermined period) measuresthe sound pressure SP or the frequency f of a sound generated by the jetemitted from the emission opening 28 of the nozzle 24 impinging on theworkpiece W when passing through the through hole H.

The controller 112 functions as the position acquisition section 78 tosequentially acquires the output data β of the sound pressure SP or thefrequency f from the measuring instrument 76, as the informationrepresenting the position x₁ of the first maximum point 32, and storesthe output data β in the storage 104. As described in connection withthe above jet observation apparatus 70, the output data β including thefirst peak value β_(max1) corresponds to the information representingthe position x₁ of the first maximum point 32.

In step S4, the controller 112 starts the laser process. Specifically,the controller 112 operates the positioning device 18 in accordance witha processing program so as to move the nozzle 24 with respect to theworkpiece W, along with which, the controller 112 performs the laserprocess (laser cutting) on the workpiece W by the laser beam emittedfrom the emission opening 28.

In step S5, the controller 112 determines whether or not the output dataβ most-recently acquired by the measuring instrument 66 is smaller thana predetermined lower limit value β_(min). This lower limit valueβ_(min) defines a boundary for determining whether or not the velocity Vof the jet emitted from the nozzle 24 is abnormally small, and ispredetermined by an operator.

In this respect, if clogging of the emission opening 28 or abnormalityin operation (e.g., out of gas) of the assist gas supply device 16occurs, the velocity V of the jet may be significantly reduced below areference value. In this case, the output data β acquired by themeasuring instrument 66 differs from (specifically, is smaller than)reference data measured by the measuring instrument 66 when the jet isnormally emitted from the nozzle 24.

The controller 112 determines whether or not the output data β issmaller than the lower limit value β_(min), whereby determining whetheror not the output data β is different from the reference data. Asdescribed above, the controller 112 functions as an abnormalitydetermination section 113 configured to determine whether or not theoutput data β is different from the reference data.

When the controller 112 determines that the output data β is smallerthan the lower limit value β_(min) (i.e., determines YES), it proceedsto step S6. On the other hand, when the controller 112 determines thatthe output data β is equal to or greater than the lower limit valueβ_(min) (i.e., determines NO), it proceeds to step S8. In step S6, thecontroller 112 sends a command to the laser oscillator 12 so as to stopa laser oscillation operation, whereby stopping the laser process on theworkpiece W.

In step S7, the controller 112 outputs an alert. For example, thecontroller 112 generates an alert signal in the form of sound or image,which indicates “There is abnormality in emission of assist gas. Checkopening dimension of nozzle or supply pressure of assist gas”. Then, thecontroller 112 outputs the alert via a speaker or a display (notillustrated). Thus, the controller 112 functions as an alert generationsection 118 configured to generate the alert.

The speaker or the display may be provided at the controller 112, or maybe provided outside the controller 112. The operator can intuitivelyrecognize from the alert that there is abnormality in the nozzle 24 orthe assist gas supply, and can replace the nozzle 24 or take measuresfor the operating abnormality (e.g., out of gas) of the assist gassupply device 16. After carrying out this step S7, the controller 112ends the flow illustrated in FIG. 14 .

In step S8, the controller 112 determines whether or not the output dataβ acquired most-recently by the measuring instrument 76 is smaller thana predetermined threshold value β_(th). This threshold value β_(th) isgreater than the above-described lower limit value β_(min). As anexample, the threshold value β_(th) may be set as a value obtained bymultiplying the first peak value β_(max1) stored in the database 106 bya predetermined coefficient a (0<a<1).

For example, if the database 106 shown in above Table 2 is used, theopening dimension ϕ is set as ϕ=1.0 mm, the supply pressure P_(s) is setas P_(s)=2.0 MPa, and the coefficient a is set as a=0.95, the thresholdvalue β_(th)=120 [dB]×0.95=114 [dB] is obtained. A relationship betweenthe output data β and position x of the process portion S of theworkpiece W with respect to the emission opening 28 is schematicallyshown in FIG. 16 . The relationship between the output data β and theposition x corresponds to the graph illustrated in FIG. 3 .

A range 116 from the threshold value β_(th) to the first peak valueβ_(max1) corresponds to a position range 114 between a position x₃ and aposition x₄. The position x₁ of the first maximum point 32 is within theposition range 114. In this respect, in above-described step S1, thenozzle 24 is disposed at the initial target position where the distanced between the emission opening 28 and the process portion S coincideswith the target distance d_(T). Accordingly, just after step S1, theprocess portion S appears to be disposed at or near the position x₁ ofthe first maximum point 32.

However, while the laser process on the workpiece W is carried out, thedistance d between the emission opening 28 and the process portion S maychange due to some factor. As such factor, there is a case where astepped portion is formed at the process portion of the workpiece W,whereby the distance d changes, for example. If the distance d changesin this way, the output data β of the measuring instrument 76 may bebelow the threshold value β_(th).

When the controller 112 determines that the output data β is smallerthan the threshold value 13th (i.e., determines YES) in this step S8, itproceeds to step S9. On the other hand, when the controller 112determines that the output data β is equal to or greater than thethreshold value β_(th) (i.e., determines NO), it proceeds to step S15.

In step S9, the controller 112 changes a target position of the nozzle24. Specifically, the controller 112 changes the target position of thenozzle 24 set at the start of this step S9 to a new target positionmoved in the z-axis negative direction or the z-axis positive direction.Then, the controller 112 functions as the movement controller 108, andoperates the positioning device 18 so as to move the nozzle 24 in thez-axis negative direction or the z-axis positive direction in order todispose the nozzle 24 at the new target position. As a result, thenozzle 24 moves closer to or away from the workpiece W.

In step S10, the controller 112 determines whether or not the outputdata β acquired by the measuring instrument 66 after step S9 increasesfrom the output data β acquired by the measuring instrument 66immediately before step S9. In this respect, if the output data βdecreases as a result of the movement of the nozzle 24 in step S9, theposition of the workpiece W (specifically, the process portion S) isseparated away from the position range 114 in the graph shown in FIG. 16. In this case, in order to bring the position of the workpiece W withinthe position range 114, it is necessary to reverse the direction inwhich the nozzle 24 is to be moved in step S9.

On the other hand, if the output data β increases as a result of themovement of the nozzle 24 in step S9, the position of the workpiece Wapproaches the position x₁ in the graph shown in FIG. 16 . In this case,it is not necessary to change the direction in which the nozzle 24 is tobe moved in step S9.

In this step S10, when the controller 112 determines that the outputdata β acquired by the measuring instrument 66 just after step S9increases from the output data β acquired by the measuring instrument 66immediately before step S9 (i.e., determines YES), it proceeds to stepS12. On the other hand, when the controller 112 determines that theoutput data β acquired by the measuring instrument 66 just after step S9decreases from the output data β acquired by the measuring instrument 66immediately before step S9 (i.e., determines NO), it proceeds to stepS11.

In step S11, the controller 112 reverses the direction in which thenozzle 24 is to be moved. For example, if the nozzle 24 has been movedin the z-axis negative direction in most-recently executed step S9, thecontroller 112 reverses the direction in which the nozzle 24 is to bemoved in next step S9 to the z-axis positive direction. Then, thecontroller 112 returns to step S9.

In step S12, the controller 112 determines whether or not the outputdata β most-recently acquired by the measuring instrument 76 is equal toor greater than the threshold value β_(th). When the controller 112determines that the output data β is equal to or greater than thethreshold value β_(th) (i.e., determines YES), it proceeds to step S15.On the other hand, when the controller 112 determines that the outputdata β is still smaller than the threshold value β_(th) (i.e.,determines NO), it proceeds to step S13.

In step S13, the controller 112 determines whether or not the number oftimes n, for which the controller 112 determines NO in step S12, exceedsa predetermined maximum number of times n_(max). This maximum number oftimes n_(max) is predetermined by the operator as an integer of 2 orgreater (e.g., n_(max)=10). When the controller 112 determines that thenumber of times n exceeds the maximum number of times n_(max) (i.e.,determines YES), it proceeds to step S14. On the other hand, when thecontroller 112 determines that the number of times n does not exceed themaximum number of times n_(max) (i.e., determines NO), it returns tostep S9.

In this way, by carrying out a loop of steps S9 to S13 in FIG. 14 , thecontroller 112 changes the target position of the nozzle 24 such thatthe output data β of the measuring instrument 76 is within the range 116of output data which represents the position range 114, during theprocess on the workpiece W, and performs feedback control for thepositioning device 18 in accordance with the changed target position soas to move the nozzle 24.

That is, the target position of the nozzle 24 is determined as apredetermined range, based on the first peak value β_(max1) of theoutput data β that represents the position x₁ of the first maximum point32. By this feedback control, the process portion S can be continuouslydisposed in the first Mach disk region 33 during the process on theworkpiece W. Thus, the first Mach disk region 33 in the laser processingsystem 110 can be defined as a region of the position range 114 definedby the threshold value β_(th).

On the other hand, when the controller 112 determines YES in step S13,in step S14, the controller 112 carries out an abnormality handlingprocess. If the output data β does not satisfy β≥β_(th) even though thefeedback control in steps S9 to S13 is repeatedly carried out for thenumber of times n_(max), the above-described abnormality such as theclogging or the out of gas may possibly occur.

In this respect, the characteristic shown in FIG. 16 is reference datameasured by the measuring instrument 76 when the jet is normally emittedfrom the emission opening 28 without occurrence of the abnormality,wherein the first peak value β_(max1) constitutes the reference data,and the threshold value β_(th) is set for the reference data. Therefore,the range 116 in FIG. 16 is a range of output data which represents theposition range 114 and which is determined based on the reference data.

If the controller 112 determines YES in step S13 by functioning as theabnormality determination section 113, the controller 112 determinesthat the output data β of the measuring instrument 76 is different fromthe reference data, and executes the abnormality handling process instep S14. This step S14 will be described with reference to FIG. 15 .Note that, in the flow illustrated in FIG. 15 , processes similar tothose of the flow illustrated in FIG. 14 are assigned the same stepnumbers, and redundant descriptions thereof will be omitted.

In step S21, the controller 112 sends a command to the assist gas supplydevice 16 so as to change the supply pressure P_(s) of the assist gas tothe chamber 29. The controller 112 increases the supply pressure P_(s)by a predetermined pressure (e.g., 0.2 MPa) in a stepwise manner, eachtime the controller 112 carries out this step S21. In this way, thecontroller 112 functions as a pressure adjustment section 115 configuredto change the supply pressure P_(s).

Then, the controller 112 carries out the above-described step S12 todetermine whether the output data β most-recently acquired by themeasuring instrument 76 is equal to or greater than the threshold valueβ_(th). The controller 112 proceeds to step S15 in FIG. 14 whendetermining YES, while it proceeds to step S22 when determining NO.

In step S22, the controller 112 determines whether or not the number oftimes m, for which the controller 112 determines NO in step S12 in FIG.15 , exceeds a predetermined maximum number of times m_(max). Thismaximum number of times m_(max) is predetermined by the operator as aninteger of 2 or greater (e.g., m_(max)=5). When the controller 112determines that the number of times m exceeds the maximum number oftimes m_(max) (i.e., determines YES), it proceeds to step S6 in FIG. 14. On the other hand, when the controller 112 determines that the numberof times m does not exceed the maximum number of times m_(max) (i.e.,determines NO), it returns to step S21.

Referring again to FIG. 14 , in step S15, the controller 112 determineswhether or not the laser process on the workpiece W has been completed,based on e.g. the processing program. When the controller 112 determinesthat the laser process has been completed (i.e., determines YES), thecontroller 112 sends a command to the laser oscillator 12 so as to stopthe laser oscillation operation, and ends the flow illustrated in FIG.14 . On the other hand, when the controller 112 determines that thelaser process has not been completed (i.e., determines NO), it returnsto step S8.

As described above, the controller 112 performs the feedback control ofthe position of the nozzle 24 such that the process portion S iscontinuously disposed in the first Mach disk region 33, based on theoutput data β acquired by the measuring instrument 76 during the processon the workpiece W. According to this configuration, even when thedistance d between the emission opening 28 and the process portion Schanges due to some factor, it is possible to perform the laser processon the workpiece W in a state where the process portion S is disposed inthe first Mach disk region 33. Thus, the assist gas can be effectivelyutilized.

Furthermore, the controller 112 determines abnormality of the emittedjet by performing step S14. If abnormality such as clogging or out ofgas occurs, the velocity V of the jet emitted from the emission opening28 hardly changes even when the supply pressure P_(s) from the assistgas supply device 16 to the chamber 29 is changed.

In this case, the output data β of the measuring instrument 76 alsohardly changes, and accordingly, the output data β does not satisfyβ≥β_(th) (i.e., it is not determined YES in step S12 in FIG. 15 ) evenwhen a loop of steps S21 to S22 in FIG. 15 is repeatedly carried out.

If the output data β does not satisfy β≥β_(th) even after the controller112 repeatedly performs the loop of steps S21 to S22 for thepredetermined number of times m_(max) by functioning as the abnormalitydetermination section 113, the controller 112 determines that the outputdata β is different from the reference data, and outputs the alertmessage in step S7 in FIG. 14 . According to this configuration, theoperator can intuitively recognize that there is abnormality in thenozzle 24 or the assist gas supply, and replace the nozzle 24 or takemeasures for the abnormality (out of gas) in operation of the assist gassupply device 16.

On the other hand, a case may occur in which the velocity V of the jetemitted from the emission opening 28 decreases slightly below thereference value due to minor abnormality, such as an error of theopening dimension or a length in the z-axis direction of the emissionopening 28, inclination of the emission opening 28 with respect to thez-axis, or a design dimension error of an interior space of the nozzle24 (chamber 29). In the case of such minor abnormality, the velocity ofthe jet varies in response to change in the supply pressure P_(s), butthe output data β may not satisfy β≥β_(th), and it may be determined YESin step S13 even when the feedback control of steps S9 to S13 isrepeatedly carried out.

According to the laser processing system 110, in step S14, thecontroller 112 continues the process on the workpiece W if the outputdata β satisfies β≥β_(th) by performing step S21. According to thisconfiguration, even when the velocity V of the jet decreases below thereference value due to the minor abnormality such as a dimensionalerror, it is possible to continue the process on the workpiece W in astate in which the jet is blown onto the process portion S at thesufficiently large velocity V, by changing (specifically increasing) thesupply pressure P_(s).

Note that, each time the controller 112 determines YES in step S12 in afirst laser process, the controller 112 may sequentially store thedistance d between the emission opening 28 and the process portion S atthis point of time. Then, the controller 112 may set the initial targetposition in step S1 of a second laser process to be carried out next tothe first laser process, based on the distance d stored in the firstlaser process. For example, the controller 112 may set, as the initialtarget position of the second laser process, an average value of thedistance d or the last stored distance d, which has been stored in thefirst laser process.

Note that, as modification of the laser processing system 110, theabove-described measuring instrument 66 may be applied, instead of themeasuring instrument 76. In this case, the measuring instrument 66 isconfigured to measure the velocity V of the jet in a non-contact manner,at the position of the process portion S (or a position slightlydisplaced from the process portion S toward the emission opening 28).The measuring instrument 66 thus applied to the laser processing system110, the positioning device 18, and the controller 112 constitute thejet observation apparatus 60 described above.

In this modification, the controller 112 can carry out the flowsillustrated in FIG. 14 and FIG. 15 based on the output data α of themeasuring instrument 66 instead of the output data β, and perform thelaser process on the workpiece W in a state where the workpiece W isdisposed in the first Mach disk region 33.

Next, a laser processing system 120 will be described with reference toFIG. 17 and FIG. 18 . The laser processing system 120 includes the laseroscillator 12, the laser processing head 14, the assist gas supplydevice 16, the positioning device 18, the dummy workpiece 64, themeasuring instrument 66, and a controller 122.

The controller 122 includes a processor and a storage (not illustrated),and controls the laser oscillator 12, the laser processing head 14, theassist gas supply device 16, the positioning device 18, and themeasuring instrument 66. The controller 122 functions as the positionacquisition section 68 described above. Thus, the positioning device 18,the dummy workpiece 64, the measuring instrument 66, and the controller122 constitute the above-described jet observation apparatus 60.

Next, operation of the laser processing system 120 will be described.First, the controller 122 acquires the information representing theposition x₁ of the first maximum point 32. Specifically, the controller122 functions as the position acquisition section 68 to acquire thetarget distance d_(T) from the first peak value α_(max1) of the outputdata α of the measuring instrument 66, using the method described inconnection with the above jet observation apparatus 60.

Then, the controller 122 disposes the nozzle 24 at the target position.Specifically, the controller 122 functions as the movement controller108 and operates the positioning device 18 so as to move the laserprocessing head 14 with respect to the workpiece W to dispose the nozzle24 at the target position where the distance d between the emissionopening 28 and the process portion S coincides with the target distanced_(T).

Then, the controller 122 operates the assist gas supply device 16 so asto supply the assist gas to the chamber 29 at the supply pressure P_(s)to emit the jet of the assist gas from the emission opening 28. Further,the controller 122 operates the laser oscillator 12 so as to emit thelaser beam from the emission opening 28, and operates the lens driver 23so as to adjust the position of the optical lens 22 in the direction ofthe optical axis O such that the focal point of the emitted laser beamis positioned at the process portion S.

In this state, the controller 122 carries out the laser process (lasercutting) on the workpiece W while operating the positioning device 18 inaccordance with the processing program so as to move the nozzle 24 withrespect to the workpiece W. At this time, the process portion S of theworkpiece W is disposed in the first Mach disk region 33 of the jet ofthe assist gas.

As described above, the controller 122 acquires the position x₁ of thefirst maximum point 32 by the jet observation apparatus 60 beforeprocessing the workpiece W, and carries out the laser process on theworkpiece W along with disposing the nozzle 24 at the target positiondetermined based on the acquired position x₁ of the first maximum point32. According to this configuration, since it is possible to dispose theprocess portion S in the first Mach disk region 33 during the process onthe workpiece W, the assist gas can be effectively utilized.

In addition, according to the laser processing system 120, even when theopening dimension ϕ) of the emission opening 28 and the supply pressureP_(s) of the assist gas are unknown, it is possible to acquire theposition x₁ of the first maximum point 32 by the jet observationapparatus 60 before processing the workpiece W, and determine the targetposition of the nozzle 24 based on the position x₁ of the first maximumpoint 32.

Next, a laser processing system 130 will be described with reference toFIG. 19 and FIG. 20 . The laser processing system 130 includes the laseroscillator 12, the laser processing head 14, the assist gas supplydevice 16, the positioning device 18, the measuring instrument 84, and acontroller 132.

The controller 132 includes a processor and the storage 104, andcontrols the laser oscillator 12, the laser processing head 14, theassist gas supply device 16, the positioning device 18, and themeasuring instrument 84. The database 106 as shown in above Table 1 isstored in the storage 104. The controller 132 functions as theabove-described position acquisition section 86. Thus, the measuringinstrument 84 and the controller 132 constitute the jet observationapparatus 80 described above.

Next, operation of the laser processing system 130 will be describedwith reference to FIG. 21 . A flow illustrated in FIG. 21 is startedwhen the controller 132 receives a processing start command from anoperator, a host controller, or a processing program. Note that, in theflow illustrated in FIG. 21 , processes similar to those of the flowillustrated in FIG. 14 are assigned the same step numbers, and redundantdescriptions thereof will be omitted.

After performing steps S1 and S2, in step S31, the controller 132 startsmeasurement of the supply flow rate V_(v) of the assist gas suppliedfrom the assist gas supply device 16 to the chamber 29. Specifically,the controller 132 sends a command to the measuring instrument 84 so asto cause the measuring instrument 84 to measure the supply flow rateV_(v), consecutively (e.g., at a predetermined period). In addition, thecontroller 132 starts measurement of the distance d between the emissionopening 28 and the process portion S. As described above, the distance dcan be acquired using a known gap sensor or the like.

After step S4, in step S32, the controller 132 acquires the position x₁of the first maximum point 32. Specifically, the controller 132functions as the position acquisition section 86 to calculate thedistance d_(c) from the emission opening 28 to the first maximum point32, as the information of the position x₁ of the first maximum point 32,using the output data V_(v) most-recently acquired by the measuringinstrument 84 and above Equation 1.

In step S33, the controller 132 determines whether or not the differenceδ between the distance d and the distance d_(c) is greater than apredetermined threshold value δ_(h). Specifically, the controller 132calculates the difference δ between the most-recently measured distanced between the emission opening 28 and the process portion S and thedistance d_(c) acquired in the most-recent step S32 (i.e., δ=d−d_(c)).

When the controller 132 determines that an absolute value of thedifference δ (i.e., |d−d_(c)|) is greater than the threshold valueδ_(th) (i.e., determines YES), it proceeds to step S34. On the otherhand, when the controller 132 determines that the absolute value of thedifference δ is equal to or smaller than the threshold value δ_(th)(i.e., determines NO), it proceeds to step S15. The threshold valueδ_(th) is predetermined by the operator. In step S34, the controller 132changes the target position of the nozzle 24. Specifically, if thedifference δ calculated in most-recent step S33 is a positive value, thecontroller 132 changes the target position of the nozzle 24 set at thestart of this step S34 to a new target position moved from the originaltarget position in the z-axis negative direction.

Then, the controller 132 functions as the movement controller 108 tooperate the positioning device 18 so as to move the nozzle 24 in thez-axis negative direction in order to dispose the nozzle 24 at the newtarget position. As a result, the nozzle 24 approaches the workpiece W,and whereby the distance d between the emission opening 28 and theprocess portion S decreases.

On the other hand, if the difference δ calculated in most-recent stepS33 is a negative value, the controller 132 changes the target positionof the nozzle 24 set at the start of this step S34 to a new targetposition moved from the original target position in the z-axis positivedirection. Then, the controller 132 operates the positioning device 18so as to move the nozzle 24 in the z-axis positive direction in order todispose the nozzle 24 at the new target position. As a result, thenozzle 24 moves away from the workpiece W, and whereby the distance dbetween the emission opening 28 and the process portion S increases.After performing step S34, the controller 132 returns to step S32.

On the other hand, when determining NO in step S33, the controller 132performs above-described step S15, in which, when determining YES, thecontroller 132 sends the command to the laser oscillator 12 so as tostop the laser oscillation operation to end the flow illustrated in FIG.21 , while it returns to step S32 when determining NO.

Thus, in the laser processing system 130, the controller 132 changes thetarget position of the nozzle 24 based on the position x₁ of the firstmaximum point 32 acquired by the jet observation apparatus 80 during thelaser process, and performs feedback control for the positioning device18 according to the changed target position to move the nozzle 24.

That is, the target position of the nozzle 24 is determined as apredetermined range (the range in which 0≤δ·δ_(th) is satisfied) basedon the position x₁ of the first maximum point 32. By this feedbackcontrol, the process portion S can be continuously disposed in the firstMach disk region 33 during the process on the workpiece W. That is, thefirst Mach disk region 33 in the laser processing system 130 can bedefined as a region of the range in which the above-mentioned differenceδ satisfies 0≤δ≤δ_(th).

According to the laser processing system 130, it is possible to carryout the laser process on the workpiece W in a state where the processportion S is disposed in the first Mach disk region 33, even when thedistance d between the emission opening 28 and the process portion Schanges due to some factor. Accordingly, the assist gas can beeffectively utilized.

Next, a jet adjustment device 140 will be described with reference toFIG. 22 . The jet adjustment device 140 is configured to adjust theposition x₁, x₂ of the maximum point 32, 34 of the jet emitted from theemission opening 28 of the nozzle 24, and includes an enclosure 142 andan enclosure driver 144. The enclosure 142 is a tubular member having aradial inner dimension.

The enclosure 142 is comprised of a flexible cylindrical member having aradius R as the radial inner dimension. The cylindrical member is madeof e.g. a bristle material, a resin material, or a rubber material.

The enclosure 142 is disposed substantially concentric with the emissionopening 28 with respect to the optical axis O, and includes an end 142 ain the z-axis negative direction and an end 142 b opposite the end 142a. The end 142 a is placed on the installation surface of the work table38. The end 142 b is disposed at a position separate away from theemission opening 28 in the z-axis positive direction. In other words,the enclosure 142 has a length in the z-axis direction sufficient todispose the end 142 b to separate away from the emission opening 28 inthe z-axis positive direction during the process on the workpiece.

The enclosure driver 144 includes a mechanism section 146 configured todeform the enclosure 142 so as to change the radius R of the enclosure142, and a power section 148 configured to generate power for drivingthe mechanism section 146. There are various embodiments as theenclosure 142 and the mechanism section 146 that can change the radiusR. Below, examples of the enclosure 142 and the mechanism section 146will be described with reference to FIG. 23 and FIG. 24 . Note that, inFIG. 23 and FIG. 24 , the enclosure 142 is illustrated by a dotted line,for the sake of easy understanding.

A mechanism section 146A illustrated in FIG. 23 is a so-called irisdiaphragm mechanism used in e.g. a camera. Specifically, the mechanismsection 146A includes a plurality of blades 150 which are driven to moveradially inward while rotating in a circumferential direction. Theenclosure 142 is coupled to an inner edge of the plurality of blades150, and is deformed to decrease or increase its radius R along with theoperation of the blades 150. The power section 148 include e.g. a servomotor, and drives the mechanism section 146A so as to decrease andincrease the radius R of the enclosure 142.

On the other hand, a mechanism section 146B illustrated in FIG. 24includes an arm 152 extending in a circumferential direction around theoptical axis O, and a gear 156 provided in an overlapping region 154 ofthe arm 152. Teeth are formed on respective circumferential surfaces ofthe arm 152 opposing to each other in the overlap region 154, whereinthe gear 156 engages the teeth. The enclosure 142 is coupled to an innercircumference of the arm 152 other than the overlap region 154.

In a state illustrated in Section (a) in FIG. 24 , the length in thecircumferential direction of the overlapping region 154 of the arm 152is large, and a slack 158 is formed in the enclosure 142. As the gear156 is rotated in one direction from the state illustrated in Section(a) in FIG. 24 , the overlapping region 154 of the arm 152 is reduced,along with which, the slack 158 of the enclosure 142 is graduallydiminished in the circumferential direction, whereby the radius R of theenclosure 142 is increased as in a state illustrated in Section (b) inFIG. 24 .

Conversely, as the gear 156 is rotated in the other direction from thestate illustrated in Section (b) in FIG. 24 , the overlapping region 154of the arm 152 is enlarged, along with which, the slack 158 of theenclosure 142 is gradually formed greater, and whereby the radius R ofthe enclosure 142 is decreased as in the state illustrated in Section(a) in FIG. 24 . The power section 148 includes e.g. a servo motor, androtates the gear 156 so as to decrease and increase the radius R of theenclosure 142.

Referring again to FIG. 22 , the jet adjustment device 140 can adjustthe position x₁ of the first maximum point 32 and the position x₂ of thesecond maximum point 34, by changing the radius R of the enclosure 142.A principle for making it possible to adjust the position x₁, x₂ of themaximum point 32, 34 in this manner will be described below.

As described above, the assist gas emitted from the emission opening 28is reflected at a boundary with outer atmosphere, and whereby the Machdisk is formed in the jet. When the enclosure 142 is installed, anatmospheric layer present between the jet and the enclosure 142 ispressed by the jet, whereby increasing particle density in theatmospheric layer.

If the assist gas is reflected at the boundary with the atmosphericlayer pressed in this manner, the reflection angle and the reflectionposition of the assist gas is changed, as a result of which, theposition of the Mach disk (i.e., the position x₁, x₂ of the maximumpoint 32, 34) formed in the jet is changed when compared to a casewithout the enclosure 142.

When the inner dimension of the enclosure 142 is changed, the volume andthe particle density of the atmospheric layer present between the jetand the enclosure 142 is changed, and whereby the position of the Machdisk formed in the jet can be changed. By making use of such aprinciple, the jet adjustment device 140 adjusts the position x₁, x₂ ofthe maximum point 32, 34 in the direction of the optical axis O.

Specifically, the jet adjustment device 140 displaces the position x₁,x₂ of the maximum point 32, 34 to downstream side of the jet (i.e., adirection away from the emission opening 28 along the optical axis O),by decreasing the radius R of the enclosure 142. On the other hand, thejet adjustment device 140 displaces the position x₁, x₂ of the maximumpoint 32, 34 to upstream side of the jet, by increasing the radius R ofthe enclosure 142.

According to the jet adjustment device 140, by changing the innerdimension (radius R) of the enclosure 142, it is possible to adjust theposition x₁, x₂ of the maximum point 32, 34 so as to dispose the processportion S in the first Mach disk region 33, in response to variation inthe distance d between the emission opening 28 and the process portion Sduring the process on the workpiece.

Further, when the radius R of the enclosure 142 is decreased in a statewhere the supply pressure P_(s) to the chamber 29 formed inside thenozzle 24 having the predetermined opening dimension ϕ is constant, theposition x₁, x₂ of the maximum point 32, 34 is displaced to downstreamside of the jet, along with the velocity V of the jet at the positionx₁, x₂ increasing. Thus, the velocity V of the jet in the Mach diskregion 33, 35 where the workpiece W is to be disposed can be increasedwithout changing the supply pressure P_(s).

In other words, even when the supply pressure P_(s) is reduced, thevelocity V of the jet in the Mach disk region 33, 35 can be maintainedby decreasing the diameter of the enclosure 142. According to thisconfiguration, since a consumption amount of the assist gas can bereduced, it is possible to reduce the cost. Note that, the enclosuredriver 144 may be omitted, and the inner dimension of the enclosure 142may be changed manually.

Next, a laser processing system 160 will be described with reference toFIG. 25 and FIG. 26 . The laser processing system 160 includes the laseroscillator 12, the laser processing head 14, the assist gas supplydevice 16, the positioning device 18, the measuring instrument 84, thejet adjustment device 140, and a controller 162.

The controller 162 includes a processor and the storage 104, andcontrols the laser oscillator 12, the laser processing head 14, theassist gas supply device 16, the positioning device 18, the measuringinstrument 84, and the jet adjustment device 140 (specifically, thepower section 148). The database 106 as shown in above Table 1 is storedin the storage 104. The controller 162 functions as the above-describedposition acquisition section 86. Thus, the measuring instrument 84 andthe controller 162 constitute the jet observation apparatus 80 describedabove.

Next, operation of the laser processing system 160 will be describedwith reference to FIG. 27 . A flow illustrated in FIG. 27 is startedwhen the controller 162 receives a processing start command from anoperator, a host controller, or a processing program. Note that, in theflow illustrated in FIG. 27 , processes similar to those of the flowillustrated in FIG. 21 are assigned the same step numbers, and redundantdescriptions thereof will be omitted.

After starting the flow illustrated in FIG. 27 , the controller 162carries out steps S1 to S33 similar to the flow illustrated in FIG. 21 .When determining YES in step S33, in step S41, the controller 162controls the position x₁ of the first maximum point 32. Specifically,when the difference δ (=d-d_(c)) calculated in most-recent step S33 is apositive value, the controller 162 sends a command to the power section148 of the enclosure driver 144 so as to decrease the inner dimension(radius R) of the enclosure 142. Due to this, the position x₁ of thefirst maximum point 32 is displaced to downstream side of the jet.

On the other hand, when the difference S calculated in most-recent stepS33 is a negative value, the controller 162 operates the enclosuredriver 144 so as to increase the inner dimension (radius R) of theenclosure 142. Due to this, the position x₁ of the first maximum point32 is displaced to upstream side of the jet.

In this way, the controller 162 functions as a maximum point controller164 configured to control the position x₁ of the first maximum point 32by changing the inner dimension of the enclosure 142 based oninformation of the position x₁ of the first maximum point 32 acquired bythe position acquisition section 86 in step S32. After executing stepS41, the controller 162 returns to step S32.

According to the laser processing system 160, it is possible tocontinuously dispose the process portion S in the first Mach disk region33 during the process on the workpiece W, by changing the innerdimension of the enclosure 142, without moving the nozzle 24. Accordingto this configuration, even when the distance d between the emissionopening 28 and the process portion S changes due to some factor, it ispossible to carry out the laser process on the workpiece W along withdisposing the process portion S in the first Mach disk region 33. Thus,the assist gas can be effectively utilized.

Note that, in the laser processing system 160, the storage 104 may storea database in which a plurality of the target distances d_(T) arerecorded in association with the opening dimensions ϕ of the nozzle 24,the supply pressures P_(s), and the inner dimensions (radii R) of theenclosure 142. In this case, in above-described step S41, the controller162 can determine a target inner dimension of the enclosure 142 byapplying the opening dimension ϕ, the supply pressure P_(s), and thedistance d_(c) calculated in step S32 as the target position distanced_(T) to the database.

Then, in step S41, the controller 162 operates the enclosure driver 144so as to change the inner dimension of the enclosure 142 to the targetinner dimension acquired from the database. As a result, it is possibleto accurately dispose the process portion S in the first Mach diskregion 33.

Further, the above-described laser processing system 130 can alsoperform the flow illustrated in FIG. 27 . In this case, in step S41, thecontroller 132 may control the position x₁, x₂ of the maximum point 32,34 by changing the supply pressure P_(s) to the chamber 29. In thisrespect, if the supply pressure P_(s) to the chamber 29 is increased,the position x₁, x₂ of the maximum point 32, 34 is displaced todownstream side of the jet (i.e., the direction away from the emissionopening 28 along the optical axis O).

On the other hand, if the supply pressure P_(s) to the chamber 29 isdecreased, the position x₁, x₂ of the maximum point 32, 34 is displacedto upstream side of the jet (i.e., the direction approaching theemission opening 28 along the optical axis O). In step S41, when thedifference δ (=d−d_(c)) calculated in most-recent step S33 is a positivevalue, the controller 132 sends a command to the assist gas supplydevice 16 so as to increase the supply pressure P_(s). Due to this, theposition x₁ of the first maximum point 32 is displaced to downstreamside of the jet.

On the other hand, when the difference δ calculated in most-recent stepS33 is a negative value, the controller 132 sends a command to theassist gas supply device 16 so as to decrease the supply pressure P_(s).Due to this, the position x₁ of the first maximum point 32 is displacedto upstream side of the jet. In this way, the controller 132 functionsas a maximum point controller configured to control the position x₁ ofthe first maximum point 32 by changing the supply pressure P_(s) basedon the information of the position x₁ of the first maximum point 32acquired by the position acquisition section 86 in step S32.

Note that, the positioning device 18 is not limited to theabove-described structure, but may include e.g. a work table movablealong the x-y plane, and a z-axis movement mechanism configured to movethe nozzle 24 along the z-axis. Alternatively, the positioning devicemay be configured to simply fix the nozzle 24 at a position with respectto the workpiece W, manually, without any movement mechanism.

Further, there are various embodiments of the dummy workpiece 64 and themeasuring instrument 66 of the jet observation apparatus 60 illustratedin FIG. 4 . Below, examples of the dummy workpiece 64 and the measuringinstrument 66 will be described with reference to FIG. 28 and FIG. 29 .In an example illustrated in FIG. 28 , the dummy workpiece 64 has acircular through hole 64 b formed at a position corresponding to theabove-described dummy process portion 64 b. The opening dimension of thethrough hole 64 b is set to be substantially the same as the openingdimension of the through hole that is estimated to be formed when theworkpiece W is perforated by the laser beam emitted from the nozzle 24.

The measuring instrument 66 includes a pair of columns 170 and ahot-wire 172. The pair of columns 170 extends from a surface 64 c of thedummy workpiece 64 in the z-axis positive direction, so as to beopposite to each other. The hot-wire 172 is linearly strained betweenthe pair of columns 170, and the resistance value thereof varies inresponse to the velocity V of the jet emitted from the emission opening28.

For example, the length L of the hot-wire 172 extending between the pairof columns 170 (i.e., the distance between the pair of columns 170) maybe set to be equal to or smaller than the opening dimension ϕ of theemission opening 28, or equal to or smaller than the opening dimensionof the through hole 64 b. Alternatively, the hot-wire 172 may becomprised of a material having high stiffness. By setting the length Lto be small or making the hot-wire 172 from the material with highstiffness in this manner, it is possible to prevent the hot-wire 172from bending when the hot-wire 172 is disposed in the jet.

Further, the distance from the surface 64 c of the dummy workpiece 64 tothe hot-wire 172 may be set to e.g. 0.5 mm or less. By setting thedistance from the surface 64 c to the hot-wire 172 to be smaller in thisway, the velocity V of the jet can be measured at a position closer tothe process portion S of the workpiece W during the laser process.

In an example illustrated in FIG. 29 , the measuring instrument 66includes a hot-wire 174 strained in the through hole 64 b. The length Lof the hot-wire 174 coincides with the opening dimension of the throughhole 64 b. The hot-wire 174 is disposed at the position of the surface64 c of the dummy workpiece 64. According to such an arrangement of thehot-wire 174, the velocity V of the jet can be measured at a positioncloser to the process portion S of the workpiece W during the laserprocess. As described above, the measuring instrument 66 in FIG. 28 andFIG. 29 constitutes a hot-wire anemometer.

Note that, in the embodiments described above, when the workpiece W isprocessed, the workpiece W may be disposed in the second Mach diskregion 35 (second maximum point 34) or in an n-th Mach disk region (n isan integer of 3 or greater). Further, instead of the above-described jetobservation apparatuses 60, 70 or 80, a high-speed camera may beemployed to capture an image as shown in FIG. 2 , and the position x₁,x₂ of the maximum point 32, 34 may be measured based on the image, forexample.

In addition, the shape of the emission opening 28 is not limited to acircular shape, but may have any shape such as a polygonal shape or anelliptical shape.

Further, the features of the various embodiments described above may becombined with each other. For example, the jet observation apparatus 80may be combined with the laser processing system 110 or 120, or the jetadjustment device 140 may be combined with the laser processing system110 or 120.

While the present disclosure has been described through specificembodiments, the above-described embodiments do not limit the inventionas defined by the appended claims.

The invention claimed is:
 1. A laser processing system comprising: anozzle including an emission opening configured to emit a jet of anassist gas along an optical axis of a laser beam, the nozzle beingconfigured to forming a maximum point of velocity of the jet at aposition away from the emission opening; a velocity sensor configured tomeasure the velocity of the jet; and a processor configured to acquireinformation representing a position of the maximum point based on outputdata of the velocity sensor.
 2. The laser processing system of claim 1,wherein the velocity sensor consecutively measures the velocity alongthe jet, wherein the processor acquires, as the information, a peakvalue of the consecutive output data output by the velocity sensor. 3.The laser processing system of claim 1, further comprising a dummyworkpiece disposed forward in a flow direction of the jet, wherein thevelocity sensor measures the velocity between the emission opening andthe dummy workpiece.
 4. The laser processing system of claim 1, whereinthe velocity sensor includes: a hot-wire anemometer configured tomeasure the velocity of the jet in a contact manner; or a laseranemometer configured to measure the velocity of the jet in anon-contact manner.
 5. The laser processing system of claim 1, furthercomprising: a movement mechanism configured to move the nozzle and aworkpiece relative to each other; and a movement controller configuredto control the movement mechanism so as to dispose the nozzle withrespect to the workpiece at a target position determined based on theinformation.
 6. A method of laser process on a workpiece using the laserprocessing system of claim 1, the method comprising emitting the jetfrom the emission opening of the nozzle and processing the workpiecewith the laser beam, while disposing the nozzle with respect to aprocess portion of the workpiece at a target position determined basedon the information.
 7. A jet observation apparatus comprising: avelocity sensor configured to consecutively measure velocity of asupersonic jet of a gas emitted from an emission opening of a nozzle,along the supersonic jet; and a processor configured to acquire, asinformation representing a position of a maximum point of the velocityof the supersonic jet, a peak value of consecutive output data output bythe velocity sensor, the maximum point being formed at the position awayfrom the emission opening, the maximum point of velocity being formed ina Mach disk region where reflected waves of an assist gas reflected at aboundary between the supersonic jet and an atmosphere outside thesupersonic jet interfere with each other.
 8. A method of observing ajet, the method comprising: consecutively measuring velocity of asupersonic jet of a gas emitted from an emission opening of a nozzle,along the supersonic jet; and acquiring, as information representing aposition of a maximum point of the velocity of the supersonic jet, apeak value of data obtained by consecutive measurement, the maximumpoint being formed at the position away from the emission opening, themaximum point of velocity being formed in a Mach disk region wherereflected waves of an assist gas reflected at a boundary between thesupersonic jet and an atmosphere outside the supersonic jet interferewith each other.